Drill string joint



Jan. 2, 1962 P. B. BARNETT DRILL STRING JOINT Original Filednec. 5. 1955FOUL 5. 542N577 IN VEN TOR.

w m an aw United States Patent 3,015,500 DRILL STRlNG JOINT Paul B.Barnett, Glendora, Calif., assignor to Dresser Industries, Inc, Dallas,Tex., a corporation of Delaware Continuation of application Ser. N550,932, Dec. 5, 1955. This application Jan. 8, 1959, Ser. No. 785,755 4Claims. (Cl. 285-47) The present invention relates to drill strings suchas are employed in drilling oil and gas wells, and more specificallyrelates to a safety joint for connecting together two lengths orsections of drill tubing. It is common practice in drilling oil or gasWells to employ a drill string comprising interconnected lengths ofdrill pipe or tubing, the junctures of which are formed of box and pinends having interfitting and complementally threaded tapered portionsadapted to be turned together to form a rigid, fluid-tight coupling orjoint. The hollow interiors of several lengths of tubing form apassageway for the downward flow of drilling fluid to the bit supportedat the lower end of the drill string, from which point the drillingfiuid returns to the top of the borehole through the annular spaceencircling the drill string.

This application is a continuation of the copending application of PaulB. Barnett, Serial No. 550,932, filed December 5, 1955, now abandoned.

Under certain conditions it is desired to produce electrical logs of theearths strata or formations as the drilling proceeds, and for thispurpose one or more of the lower drill collar sections of tubing may beinsulated from the remainder of the drill string and/ or the drill bit.Insulation is effected by covering the interior and exterior of aportion of one or more of the drill collar sections with an insulatingmedium such as a rubber coating, and by providing an insulating mediumin one or both of the joints contained in the insulated length of thedrill string. Due to the extremely adverse environmental conditionsunder which the lower end of the drill string operates in drilling,considerable difi'iculty has been experienced with such insulatedjoints, the joints becoming loosened or failing completely, thusresulting in occasional expensive fishing operations. Further itsometimes occurs that a drill bit will become stuck or hung up for ashort period of time, during which the drill string winds up as atorsion spring and builds up sufi'lcient torque to free the drill bit,following which the drill bit and lower portion of the drill string arerotated at an'unusually high rate of speed which may cause the drill bitto spin oil the lower end of the drill string. This, too, necessitates afishing job which involves a complete round trip with the drill string.

The present invention provides means for overcoming the mentioneddifiiculties experienced with conventional drill string joints, whetherof the insulated or not-insulated type. The invention provides meanswhereby when a joint becomes loosened or fails, the two tubing sectionsforming the faulty joint remain mechanically connected by an auxiliarymeans which permits withdrawal of the lower section of tubing along withthe upper section and eliminates the expensive fishing job. The presentinvention is particularly adaptable to plain tapered joints and topin-connected joints, but is also suitable for conventional box and pinthreaded joints, as will become evident from a consideration of thefollowing specification. To illustrate the principles of the invention,it is herein illustrated and disclosed in connection with a conventionalthreaded box and pin joint and a plain tapered insulated joint. It willbe understood, however, that the invention is applicable to othersuitable types of drill string element joints.

Referring now to the drawings forming a part of this specification,

FIGURE 1 is a view in elevation of a drill string tubing joint ofmodified box and pin type, with means according to the present inventionapplied thereto, and with portions broken away and parts shown insection;

FIGURE 2 is a view in elevation of a plain taper drill string tubingjoint of the insulated type, with means according to the presentinvention applied thereto, portions having been removed for purposes ofillustration, and with some parts being shown in section; and

FIGURE 2A is a view of a portion of FIGURE 2 enlarged, better toillustrate the arrangement of various parts thereof.

Referring now to FIGURE 1, there are shown upper and lower elements orsections 12 and i4, respectively, of conventional drill string joined ina conventional box and pin type joint. The upper section 12 has a lowerthreaded tapered portion 16 which has been stabbed into and turned intotight joining relation with the upper internally threaded portion 18 ofsection 14. While the joint thus far described may be as illustrated,that existing between adjacent interconnected sections of drill stringtubing, it will be understood that the joint may as well be thatexisting between a section of tubing and a drill collar, or thatexisting between a section of drill tubing or drill collar and a drillbit, or other drill string elements, such joints being of similar formand construction, as is well understood in the art. Due to the extremedegree of shock and vibration incident to contact and relative motion ofthe drill bit and drill string with respect to the earth formation, and/or the high torsional stresses to which drill string is subjected, anyof the joints may become loosened or otherwise fail in service. When thetwo elements of drill string forming the joint thus separate or fail inservice, further drilling with the rig cannot be accomplished until thedefective elements have been replaced. The upper portion of thedisjointed drill string is removed, and the lower portion is then fishedout by special apparatus, as is well understood in the art.

The means provided by the present invention eliminates all phases andaspects of the mentioned type of fishing operation, and reducesreplacement of the detective joint to a mere pulling of the drill stringsufiicient to expose the defective joint at the top of the borehole,replacement of the defective elements, and return of the string intoplace. In accordance with the present invention, and as depicted inFIGURE 1, the upper section 12 of drill string is provided with one ormore recesses and preferably a single peripheral recess 2%) extendingaround its exterior adjacent to but spaced from the threaded portion 16;the recess being preferably of the cross-sectional shape and form thereshown. The lower section 14- of drill string is provided with one ormore similar recess means, and preferably with a single annular recess22 adjacent to but suitably spaced from the threaded portion 13. A splitsleeve structure, indicated generally by ordinal 24, and which maycomprise one, two or more longitudinally extending sections, is formedand arranged with shaped internal projections such as are indicated at26 and 28, adapted to fit in and engage in respective recesses 26 and 22in a manner and fashion shown in the left portion of FIGURE 1, when thesleeve structure is in assembled form closely encircling the joinedportions in and 18 of the respective drill string elements. Preferablythe split sleeve structure 24 is formed of material of relatively hightensile strength and is such as to closely engage the exterior surfacesof the appropriate portions of sections 12 and 14 when assembled. Thesplit sleeve structure when applied to the joined ends of sections 12and 14 and with its projections 26 and 28 engaged in the respectiverecesses 29 and 22, is adapted to be maintained in assembled relation bysuitable means, preferably in the form of high tensile retaining ringsor bands 36 and 32 encircling, respectively, the upper and lower ends ofthe sleeve structure. The retaining bands may be and preferably aresecured in retaining position by suitable means such as, for example,countersunk screws 34 fitted through suitable apertures in therespective rings and engaging in complementary tapped aperatures formedin reduced diameter end portions of the sleeve element or elements asindicated in FlGURE l. The recesses formed in sections 12 and lid forreception of the projections 26 and 28 of t e sleeve structure arepreferably formed with undercut faces at these ends adjacent therespective tubing ends, as indicated in the section View in the lefthand part of FIGURE 1, and the projections such as 26 and 23 are formedwith complementary undercut portions. Also, preferably but notnecessarily, the sleeve structure is urged or biased into contactingrelation with one or the other of the notched or undercut sections orportions of the respective recesses by suitable means such as by a ringor'band of flexible material 36 encircling one of the tubing sectionsand held in place by an overlapping portion of a respective one of theretaining bands 3% or 32 (in the illustrated embodiment by retainingband 32). It will be evident that the sleeve structure, formed andassembled in place as described and indicated, serves as a means tomechanically interconnect the drill string elements 12 and 14 in the eent of loosening or failure of their threaded interconnecttion. If thethreads of either the box or pin or both fail, the weight normallysupported by upper section 12 is transferred from the joint to thesleeve structure 24 by slight upward relative movement of section l2with respect to section 14 and concurrent interengagement or" theprojection or projections as of the sleeve structure with thecomplementally formed lower faces of the recess 29 formed in uppersection 12. lt will'be understood that the material and dimensionsof-the sleeve part or parts are made such that the sleeve structure isenabled to thus bear the burden transferred to it. As hereinbeforenoted, the sleeve structure may comprise one, two, or more, principal.longitudinally extending elements, but preferably comprises two suchelements, of such dimensions as to closely encircle and bear against thejunctureforming portions of the two drill string elements. The splitsleeve structure 24 may be maintained in the assembled form againstoutward expansion or displacement by both the bands 3i) and 32 and byone or more of the coacting complementally formed surfaces of theprojections 2-6 and 23 and respective recesses 20 and 22.

Referring now to FIGURE 2, there is depicted an application of thepresent invention to a form of drill string tubing joint of theinsulated type wherein the upper and lower sections of drill stringtubing are electrically insulated one from the other. While the type ofinsulated tubing joint depicted is of the plain tapered species, it willbe understood that the present invention may equally well be applied toa wide variety of insulated drill string element joints. In FlGURE 2 anupper drill string tubing section 52 is joined to a lower drill stringtubing section 54 by a plain tapered insulated joint comprising a lowertapered portion 56 of upper section 52 and a comple mentally taperedupper portion 53 of tubing section 54, the two portions 55 and 53 beingelectrically isolated, one from the other, by a coating or layer ofelectrical insulation 6 1?. The electrical insulation 69 may be in theform of a coating applied to either or both of the portions 56 and 53,or may comprise a separate shell-like member of suitable materialinstalled in the shell of portion 58 prior to the stabbing in of portion55 and pressed into firm contact with both portions 56 and 58 as thoseportions are assembled with the application of great longitudinal compressive force on the tubing sections. Preferably, but not necessarily,the insulated joint comprises an internal jacket or covering ofinsulation oz extending over a more or less extensive portion of thebore of the drill string adjacent the joint. According to the presentinvention, the upper and lower drill string sections 52 and 54 areprovided with recesses, preferably peripheral in form, and

indicated generally at 64 and 66, respectively, similar in form andcharacteristics to the previously described recesses 2b and 22 shown inFIGURE 1. A split sleeve structure is provided, indicated generally byordinal and comprising one or more principal longitudinally extendingelements and such element or elements having upper and lower internalprojections such as ill and 72, respectively, adapted to repose in therespective recesses 64 and es, as indicated. The lower internalprojection or projections 72, are, as indicated, arranged to closely litin respective complementary recess or recesses 66; whereas recess meanso l and one or more complementary projection or projections 7d are sorelatively formed as to provide clearance "and complete lack of contactbetween the projection or projections and any part of upper tubingsection 52. To this end an appropriate portion of the length of uppertubing section 52 is relieved, as for example, at 7 3 and 75, wherebythe sleeve structure, when assembled and mounted in encircling relationaround the jointed ends of sections 52 and 54, is completely out ofelectrical contact with section 52. This insulated status of the sleevestructure and section 52. is maintained in normal operation of the drillstring by a layer of electrical insulation 78 applied over theappropriate outer surface area of tubing section 52. The longitudinallyextending element or elements of sleeve structure 6%? are maintained inassembled relationship by a plurality of encircling, prefrably endless,bands and 82 appropriately secured in any suitable manner to the sleeveelement or elements, as, for example, by countersunk screws 34 asindicated. The sleeve in assembled relationship encircling the jointedlower end of tubing section 52 and upper end of tubing section 54 ispreferably maintained with its lower projections 72 in close contactingrelationship with a complementally form d upper portion of the wall ofrecess means 65 by a means interposed in the lower portion of recess 66;such means being in the form, for example, of one or more G-rings, or awrapping of steel wire 8 which means may be held in place by lowerband32 as indicated. From a consideration or" the structure depicted in FlG-URE 2 and so far described, it will be evident that while the sleevestructure as may be in intimate electrical contact with tubing section54, it is nevertheless electrically isolated from the tubing section 52by an interposed layer of electrical insulation, thus leaving sections52 and 54 electrically isolated, each from the other. As may be usual, aportion of the outermost surface of the lower end of tubing section 52and ofthe upper end of tubing section 5'4 may be electrically insulated,each from the other and from electrically conductive borehole fluids bymeans of a coating or jacket of electrical insulation d6 appliedtherearound subsequent to the assembly of the split sleeve structurearound the joint. Thus it is evident that if the joint formed by the boxportion 53 of tubing section 5 and the pin portion 56 of tubing section52 fails, the load normally supported through the joint will betransferred to the sleeve structure 63, and although the insulation mayfail, the upperand lower tubing sections will remain mechanicallyinterconnected, whereby the lower section and any parts supportedthereby may be removed from the borehole without a fishing operation.

From the preceding description and explanation it will be seen that theinvention provides a safety joint for drill string tubing which permitstwo previously joined drill string elements to remain. mechanicallyinterconnected after failure of their joint, whereby the lower drillstring element may be removed from the well or borehole without thetrouble, expense and lesser time involved in a fishin operation. Whilethe particular means and joints used to illustrate a preferredembodiment of the invention are of two specific types, it will beevident to those skilled in the art that the principles of the inventionare applicable to a wide variety of constructions and types of drillstring joints. Accordingly, it is not desired to be limited to theprecise details of the illustrated physical embodiments of theinvention, but what is claimed is:

1. A drill string joint including in combination: a pair ofoppositely-positioned body members including complementarily formed boxand pin members thereof interconnected in telescoping, end-to-endcoaxial and normally rigid engagement; an external, annular grooveformed coaxially around the exterior of each of said body membersadjacent said box and pin members such grooves each being formed withthe faces nearest the said box and pin members undercut; alongitudinally extending split sleeve member encircling said box and pinmembers and said body portion; longitudinally spaced-apart, inwardlyprojecting lug members, of a longitudinal width less than thelongitudinal width of the said grooves and having undercut end portionsadapted to fit the aforesaid underout faces of said grooves, attached tosaid sleeve member and extending into the grooves; a flexible ringfitting into one of the grooves between a side thereof and one of saidlugs and in close engagement therewith, said ring biasing said sleevemember longitudinally so that said lugs are urged against sides of thegroove into which they fit thereby being effective to retain said bodymembers against substantial longitudinal movement with respect to oneanother in event of failure of the normally rigid joint between said boxand pin members; retaining bands extending around said sleeve member andfitting over at least a portion of each of said lugs; and means holdingsaid bands on said sleeve in close engagement with said lugs.

2. A drill string joint including in combination: a pair ofoppositely-positioned body members including complementarily formed,threaded box and pin members thereof threaded together in telescoping,end-to-end coaxial and normally rigid engagement; means forming anexternal annular groove formed coaxially around the exterior of each ofsaid body members adjacent said box and pin members such grooves eachbeing formed with the faces nearest the said box and pin members undercut; a longitudinally extending split sleeve member encircling said boxand pin members and said body portion; longitudinally spaced-apartinwardly projecting lug members, of a longitudinal width less than thelongitudinal width of the said grooves and having undercut end portionsadapted to fit the aforesaid undercut faces of said grooves, attached tosaid sleeve member and extending into the grooves; a flexible ringfitting into one of the grooves between a side thereof and one of saidlugs and in close engagement therewith, said ring biasing said sleevemember longitudinally so that said lugs are urged against sides of thegroove into which they fit thereby being effective to retain said bodymember against substantial longitudinal movement with respect to oneanother in event of failure of the normally rigid threaded joint between said box and pin members while permitting relative rotationtherebetween; retaining bands extending around said sleeve member andfitting over at least a portion of each of said lugs; and means holdingsaid bands on said sleeve in close engagement with said lugs.

3. A drill string joint including in combination: a pair ofoppositely-positioned body members including complementarily formed boxand pin members thereof interconnected in telescoping, end-to-endcoaxial and normally rigid engagement; an external, annular grooveformed coaxially around the exterior of each of said body membersadjacent said box and pin members; a layer of insulating materialpositioned between said box and pin members and within at least one ofthe grooves and effective to electrically isolate said body members fromone another; a longitudinally extending split sleeve member encirclingsaid box and pin members and adjacent portions of each of said bodymembers; longitudinally spacedapart, inwardly projecting lug members, ofa longitudinal width less than the longitudinal width of the saidgrooves, attached to said sleeve member and extending into the saidgrooves; a flexible ring fitting into one of the grooves between a sidethereof and one of said lugs and in close engagement therewith, saidring biasing said sleeve member longitudinally so that said lugs areurged toward sides of the grooves into which they fit thereby beingeffective to retain said body members against substantial longitudinalmovement with respect to one another in event of failure of the normallyrigid joint between said box and pin members while permitting relativerotation therebetween; retaining bands extending around said sleevemember and fitting over at least a portion of each of said lugs; andmeans holding said bands on said sleeve in close engagement with saidlugs.

4. A drill string joint including in combination: a pair ofoppositely-positioned body members including complementarily formed boxand pin members thereof interconnected in telescoping, end-to-endcoaxial and normally rigid engagement; an external, annular grooveformed coaxially around the exterior of each of said body membersadjacent said box and pin members; a layer of insulating materialpositioned between said box and pin members and within at least one ofthe grooves, an internal jacket of insulating material on the internalbores of said body members and coextensive with the joint therebetween,sm'd layer and jacket being eifective to electrically insulate said bodymembers from one another; a longitudinally extending split sleeve memberencircling said box and pin members and adjacent portions of each ofsaid body portions; longitudinally spaced apart, inwardly projecting lugmembers, of a longitudinal width less than the longitudinal width of thesaid grooves, attached to said sleeve member and extending into thegrooves; a flexible ring fitting into one of the grooves between a sidethereof and one of said lugs and in close engagement therewith, saidring biasing said sleeve member longitudinally so that said lugs areurged toward sides of the groove into which they fit thereby beingeifective to retain said body members against substantial longitudinalmovement with respect to one another in'event of failure of the normallyrigid joint between said box and pin members while permitting relativerotation therebetween; retaining bands extending around said sleevemember and fitting over at leut a portion of each of said lugs;

and means holding said bands on said sleeve in close.

engagement with said lugs.

References Cited in the file of this patent UNITED STATES PATENTS Re.21,606 Nielsen Oct. 22, 1940 391,313 Gordon Oct. 16, 1888 1,043,806 DahlNov. 12, 1912 1,738,021 Shipley Dec. 3, 1929 1,790,266 Fullmer Jan. 27,1931 2,267,168 Posey Dec. 23, 1941 2,795,398 Ragland June 11, 1957FOREIGN PATENTS 738,569 France Dec. 27, 1932 745,184 France May 6, 1933508,498 Great Britain June 30, 1939

